Investigation on phase separation kinetics of polyolefin blends through combination of viscoelasticity and morphology.

Phase separation kinetics of polyethylene copolymer blends polyethylene-co-hexene (PEH)/polyethylene-co-butene (PEB) at a phase separation temperature of 130 °C have been investigated through the combination of rheological measurements and optical microscope observation. When the blends are located in the unstable region, i.e., PEH/PEB 40/60 blend (H40), 50/50 blend (H50), and 60/40 blend (H60), due to the coeffect of the fast decay of concentration fluctuations and the reduced interfacial area, the stroage modulus, G′, behaves dramatically, decreasing at the early or intermediate stages; while when the blends are located in the metastable region, i.e., PEH/PEB 70/30 blend (H70), G′ decreases slightly and slowly during the whole time sweep process. During the cyclic frequency sweeps, G′ evolutions of H50 and H70 show similar trends. Obviously different from the strong phase segregation systems, the increase of G′ with time in the metastable region has not been observed, possibly due to the entanglement ef...